Middle+
¿Cómo realizar una inyección de ViewModel usando Dagger?
sobes.tech AI
Respuesta de la IA
- Crear una clase
ViewModely marcarla con@Injectable. - Crear un
ViewModelProvider.Factoryque sepa cómo crear instancias deViewModel. Normalmente, esto se hace mediante un mapeo deClass<? extends ViewModel>aProvider<? extends ViewModel>. - Definir en un módulo de Dagger cómo crear el
ViewModelProvider.Factory. Frecuentemente se usa@Bindspara enlazar unViewModelespecífico con su@Provider. - Inyectar en la Activity o Fragment el
ViewModelProvider.Factoryy usarlo para obtener la instancia deViewModel.
// MyViewModel.java
public class MyViewModel extends ViewModel {
private final SomeDependency dependency;
@Inject
public MyViewModel(SomeDependency dependency) {
this.dependency = dependency;
}
// ... métodos de ViewModel
}
// ViewModelFactory.java
public class ViewModelFactory implements ViewModelProvider.Factory {
private final Map<Class<? extends ViewModel>, Provider<ViewModel>> creators;
@Inject
public ViewModelFactory(Map<Class<? extends ViewModel>, Provider<ViewModel>> creators) {
this.creators = creators;
}
@NonNull
@Override
public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
Provider<? extends ViewModel> creator = creators.get(modelClass);
if (creator == null) {
for (Map.Entry<Class<? extends ViewModel>, Provider<ViewModel>> entry : creators.entrySet()) {
if (modelClass.isAssignableFrom(entry.getKey())) {
creator = entry.getValue();
break;
}
}
}
if (creator == null) {
throw new IllegalArgumentException("unknown model class " + modelClass);
}
try {
return (T) creator.get();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
// ViewModelModule.java
@Module
public abstract class ViewModelModule {
@Binds
abstract ViewModelProvider.Factory bindViewModelFactory(ViewModelFactory factory);
@Binds
@IntoMap
@ViewModelKey(MyViewModel.class)
abstract ViewModel bindMyViewModel(MyViewModel viewModel);
// Agrega otros ViewModels aquí usando @Binds y @ViewModelKey
}
// ViewModelKey.java
@MapKey
@Retention(RetentionPolicy.RUNTIME)
public @interface ViewModelKey {
Class<? extends ViewModel> value();
}
// MyActivity.java
public class MyActivity extends AppCompatActivity {
@Inject
ViewModelProvider.Factory viewModelFactory;
private MyViewModel myViewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
AndroidSupportInjection.inject(this); // Si se usa dagger-android
super.onCreate(savedInstanceState);
// ...
myViewModel = new ViewModelProvider(this, viewModelFactory).get(MyViewModel.class);
// ...
}
}